1. Field of the Invention
This invention is generally directed to devices for interfacing a computer modem or a modem connected to a computer to a conventional telephone of the dual tone multiple frequency (DTMF) type so that a computer may be directly linked to the transmitter circuitry of the conventional telephone and more particularly to an interface adaptor which connects the input/output jack of a modem directly to the conventional plug which normally connects a telephone to a telephone handset. The adaptor of the present invention permits a modem to be connected in place of the standard telephone handset and thereby allows a computer to communicate directly through a conventional telephone even in instances where the telephone is a multiline telephone. The adaptor has the benefit of being very compact and requires no active electronic components and can be placed into operation without modification or disassembly to any portion of the telephone other than disconnecting the plug associated with the telephone handset and connecting the handset plug to one end of the adaptor of the present invention.
In two embodiments of the present invention, the adaptors are designed to be utilized with conventional modems however, in a separate embodiment the adaptors require a modification to the modem by providing an additional telephone input/output jack which will directly receive the plug normally used to connect the telephone handset cord to the handset.
2. History of the Related Art
With the advent of the newer laptop portable type computers, it is important to provide means for easily accessing the computers to conventional telephone systems including multiline telephone systems found in most offices and in many homes. In order to allow a computer to be interfaced with a telephone system so that digital information could be transmitted and received through the telephone system, it was originally necessary to provide a modem which would be wired or connected directly to a dedicated or single telephone line. A computer could then be connected through the modem so that digitally modulated signals could be transmitted through the modem to the dedicated telephone line. This type of dedicated line system is not satisfactory for computers of the portable type as such computers must be accessible to telephone lines at any number of sites or locations.
Due to the problem of dedicating a phone line to the modem to which a computer is connected, efforts have been made to provide switches or connectors which allow the computer modem to be connected through any one of the multilines associated with a multiline telephone system so that each of the lines can be utilized to transmit either voice or data as is necessary. Such systems avoid the need to dedicate an incoming line specifically for data transmission.
One prior method of directly connecting a modem to a multiline telephone system provided a portable modular jack which connected the modem directly in place of the transmitter microphone associated with a telephone handset. Such modular jacks are not efficient in that they require the disassembly of the mouth piece portion of the conventional telephone handset and the replacement of the transmitter with the connector associated with the modular jack. In addition, such connectors are not universally adaptable to be used with differing types or shapes of microphone transmitters found in varying types of conventional telephone handsets.
Another type of modem/telephone connector is disclosed in U.S. Pat. No. 4,543,450 to Brandt. The patent discloses an integrated connector and modem wherein the connector includes a housing in one end thereof in which a special modem is located so that the modem may be physically and electrically connected to the data terminal of a computer. The modem installed in the housing is connected through a telephone cable to a plug which is designed to plug into the telephone base unit in place of the telephone handset and its associated cable. In the patent, two wires are connected from the modem demodulator to the receiving circuitry in the telephone base unit while an additional two wires are used to connect the modem modulator to the transmitting circuitry in the telephone base unit. Such a connector or adaptor requires that the modem be contained integrally within the adaptive unit and therefore requires power from the computer terminal to energize the modem circuitry within the adaptor unit. The modem portion of the Brandt adaptor will therefore unnecessarily duplicate the function of a modem commonly found mounted within a laptop computer and also adds additional weight and space requirements. The Brandt connector or adaptor requires that the modem mounted within the adaptor housing be specially wired to make a four wire connection between the adaptor and the telephone and uses two wires for transmitting data and two wires for receiving incoming signals. Thus, the conventional telephone is utilized to separate the data into incoming and outgoing signals.